The present invention relates to a novel fluorine-containing polymeric compound which is useful as a material of Langmuir-Blodgett's films as well as to a method for the preparation of such a fluorine-containing polymeric compound.
It is known that polymeric compounds modified with long-chain perfluoroalkyl groups have excellent properties such as water- and oil-repellency, insusceptibility to dust deposition, corrosion resistance and the like so that they are used, for example, for protection and surface modification of electronic circuit boards. Further, they are promising as a material of oxygen-permeable membranes having improved selectivity for the permeation of oxygen relative to other gases by virtue of the high affinity of the perfluoroalkyl groups to oxygen.
A problem in the use of such a polymeric compound having perfluoroalkyl groups introduced into the molecular structure is that the polymer is hardly soluble in solvents due to the water- and oil repellency inherent in the perfluoroalkyl groups so that fluorine-containing polymers are generally not handleable as a material of thin films. In other words, fluorine-containing polymeric compounds can be shaped only with great difficulties into an extremely thin film as an essential element when the polymer is used as a material for surface modification or protection of boards. While it is important that the perfluoroalkyl groups as the functional groups for the oil- and water-repellency and other useful surface properties are oriented toward the surface of the polymeric material in order that the desired performance of surface modification and oxygen permeation can be fully exhibited, a general understanding is that control of such an orientation of polymeric molecules is far from possibility.
One of the inventors has been successful in preparing an ultra-thin film of a controlled molecular orientation by the Langmuir-Blodgett's method from a polyallylamine or polyvinylamine modified with perfluoroalkyl groups as bonded through an amide linkage (see, for example, Japanese Patent Kokai 63-170405. These perfluoroalkyl-modified polyallylamines or polyvinylamines, however, are still not quite satisfactory because the polymer in a solution is subject to gradual hydrolysis of the amide linkages and difficulties are encountered in the handling thereof due to the low solubility of the modified polymer in a solvent.